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62 lines
2.7 KiB
HTML
62 lines
2.7 KiB
HTML
<html>
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<head>
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<title>PostGIS Buffer Plugin</title>
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</head>
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<body>
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<center>
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<h2>QGIS PostGIS Buffer Plugin 0.1</h2>
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<h3>Documentation</h3>
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</center>
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The buffer plugin creates a user specified buffer around features in a PostGIS
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layer.
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The results of the buffer operation are stored in a new layer in the PostgreSQL
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database.
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<p>
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The plugin requires GEOS support compiled into PostGIS and the GEOS library
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must be installed (see <a href="http://geos.refractions.net">
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http://geos.refractions.net</a> for details).
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<p>
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<h3>Settings</h3>
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<center>
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<img alt="" src="bufferdialog.png"><p>
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</center>
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The options available in the buffer dialog are described in the table below.
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<center>
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<table cellpadding=4 border=1>
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<tr><th>Setting</th><th>Explanation</th></tr>
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<tr><td>Buffer distance in map units</td><td>The size of the buffer</td></tr>
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<tr><td>Table name for the buffered layer</td><td>This name will be used when creating the buffered layer in the database</td></tr>
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<tr><td>Spatial reference ID</td><td>The id from the spatial_references table that describes the coordinate system of the data</td></tr>
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<tr><td>Geometry column</td><td>Name for the column to store the geometry for each buffered feature</td></tr>
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<tr><td>Unique field to use as feature id</td><td>Name of the field to use as the primary key for the buffered layer. Select a field name from the list or choose <i>Create unique object id</i> to have the plugin create a primary key field</td></tr>
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<tr><td>Schema</td><td>Choose the schema to use in creating the buffered layer. Only existing schemas are displayed in the drop-down box</td></tr>
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<tr><td>Add the buffered layer to the map?</td><td>Checking this option will cause the buffer layer to be added to the map after processing is complete</td></tr>
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</table>
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</center>
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<h3>Howto</h3>
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To create a buffer:
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<ol>
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<li>Start QGIS
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<li>Add a PostgreSQL/PostGIS layer (this example uses the Alaska layer)
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<br>
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<img alt="" src="alaska_pglayer.png"><p>
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<li>Select the layer by clicking on it in the legend
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<li>Select Tools|Plugin Manager from the menu
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<li>From the Plugin Manager, click the box to the left of the Geoprocessing plugin
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<br><img alt="" src="pluginmanager.png"><p>
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<li>Click Ok to load the plugin
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<li>A new menu (Geoprocessing) is added to the menu bar and a Buffer icon is added
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to the toolbar.
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<li>Click on the Buffer icon <img src="buffericon.png" align="absmiddle"> in the toolbar
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<li>The Buffer dialog appears. Set the buffer distance to the desired size (example 1000)<br>
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<img src="buffer.png">
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<li>Clicking the <i>Add buffered layer to the map?</i> will cause the layer to be added as
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soon as the buffer is complete. The buffered layer can also be added to the map using the
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<i>Add a PostGIS</i> toolbar button.
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<p>
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<img src="bufferresult.png">
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</ol>
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</body>
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</html>
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